System and method for determining the location of a station in a wireless environment

ABSTRACT

A system for quantifying the shadow fading observed in a wireless environment having multiple wireless access points is also provided. A distance determination module is in signal communication with the wireless access points. The distance determination module determines a distance between a pair of the wireless access points based on location information that relates to the locations of the wireless access points at the wireless environment. A shadow fading determination module is also in signal communication with the wireless access points. The shadow fading determination module determines a shadow fading factor based on the distance between a pair of the wireless access points and based on RSS information received from one of the wireless access points in the pair of wireless access points.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/242,710 entitled “SYSTEM AND METHOD FORDETERMINING THE LOCATION OF A STATION IN A WIRELESS ENVIRONMENT”, filedon Sep. 13, 2011, by inventors Alan Jeffrey Hand and James Kirk Mathews,issued as U.S. Pat. No. 9,055,450 on Jun. 9, 2015, the contents of whichare incorporated herein by reference in its entirety.

BACKGROUND

Network administrators may desire to keep track of stations associatedwith wireless access points on a wireless network. Additionally, networkadministrators may desire to pinpoint the location of stations in awireless environment. Tracking and localizing a station in a wirelessenvironment may be difficult, however, due to the nature of wirelesscommunications. The physical properties and characteristics of thewireless environment may affect the propagation of the wireless signalsthrough the wireless environment. Additionally, conventional wirelessaccess points may not be able to determine the position of a stationrelative to the wireless access points. Therefore, there exists a needfor an improved approach to determining the location of a station in awireless environment.

SUMMARY

A computer-implemented method of quantifying the shadow fading observedin a wireless environment having multiple wireless access points isprovided. Location information relating to locations of the wirelessaccess points at the wireless environment is received. The distancebetween a pair of the wireless access points is determined based on thelocation information. A shadow fading factor is determined based on thedistance between the pair of the wireless access points and based onreceived signal strength (RSS) information received from one of thewireless access points in the pair of wireless access points.

A system for quantifying the shadow fading observed in a wirelessenvironment having multiple wireless access points is also provided. Adistance determination module is in signal communication with thewireless access points. The distance determination module determines adistance between a pair of the wireless access points based on locationinformation that relates to the locations of the wireless access pointsat the wireless environment. A shadow fading determination module isalso in signal communication with the wireless access points. The shadowfading determination module determines a shadow fading factor based onthe distance between a pair of the wireless access points and based onRSS information received from one of the wireless access points in thepair of wireless access points.

A computer-implemented method of localizing a station in a wirelessenvironment having multiple wireless access points is also provided. Ashadow fading factor for the wireless environment is determined.Respective distances between the station and the wireless access pointsis determined based on the shadow fading factor for the wirelessenvironment and based on RSS information received from the wirelessaccess points. A sub-region in the wireless environment that the stationis located in is identified. A location associated with the sub-regionthat corresponds to an approximate location of the station at thewireless environment is also identified.

A system for localizing a station in a wireless environment havingmultiple access points is further provided. A shadow fadingdetermination module determines a shadow fading factor for the wirelessenvironment. A distance determination module determines respectivedistances between the station and the wireless access points based onthe shadow fading factor and based on RSS information received from thewireless access points. A localization module identifies a sub-region inthe wireless environment based on the distances and identifies alocation associated with the sub-region that corresponds to anapproximate location of the station at the wireless environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of an implementation of a wireless array having amagnetometer.

FIG. 2 is an example of an implementation of a network management systemin signal communication with wireless arrays in the wirelessenvironment.

FIG. 3 is a flowchart of example methods steps for determining anaverage shadow fading factor for a wireless environment.

FIG. 4 is an example of a wireless environment having three wirelessarrays illustrating an approach to determining the location of a stationin a wireless environment having three or more wireless arrays.

FIG. 5 is a flowchart of example method steps for determining thelocation of a station in a wireless environment where the wirelessenvironment includes three or more wireless arrays.

FIG. 6A is an example of a wireless environment having two wirelessarrays illustrating another approach to determining the location of astation a wireless environment having two wireless arrays.

FIG. 6B is an example set of data points and the potential trianglesthat may be formed from the subsets of three data points for the set ofdata points.

FIG. 7 is a flowchart of example method steps for determining thelocation of a station in a wireless environment where the wirelessenvironment includes two wireless arrays.

DETAILED DESCRIPTION

A system and method for determining the location of a station in awireless environment is provided. The task of determining the locationof a station in a wireless environment may be referred to as stationlocalization. The system and method provided may be used to determinethe location of a station relative to two or more wireless arrays in awireless environment. Determining the location of a station in awireless environment may be advantageously improved by determining ashadow fading factor for the wireless environment as discussed furtherbelow. Additionally, various approaches may be employed to determine thelocation of a station depending on whether the wireless environmentincludes two or more than two wireless arrays.

Wireless Arrays

A wireless array is a type of wireless access device (or access point).In this example, a wireless array has multiple transceivers forexchanging wireless communications with a station. Referring to FIG. 1,an example of a wireless array 100 is shown. The wireless array 100, inthis example, includes eight transceivers T1-T8. The wireless array 100may include an alternative number of transceivers such as, for example,four transceivers, twelve transceivers, or sixteen transceivers. Eachtransceiver T1-T8 of the wireless array, in this example, is in signalcommunication with a corresponding antenna 102. Each transceiver T1-T8is also in signal communication with a controller 104 such as, forexample, a media access controller (MAC) that manages the wirelesscommunications exchanged between a station and a transceiver T1-T8 ofthe wireless array 100. The wireless array 100 may be in signalcommunication with a station (and vice versa) when the devices transmitwireless signals within range of each other such that the devices canhear each other (i.e., receive the transmitted wireless signals).

The wireless array 100 in this example also includes a magnetometer 106that determines the spatial orientation of the wireless array relativeto a magnetic field (e.g., the magnetic field of the Earth). In thisway, the magnetometer 106 of the wireless array 100 may determine thespatial orientation of the wireless array relative to, for example, thesurface of the Earth based on the Earth's magnetic field. Themagnetometer 106 may be any form of sensor capable of determining thespatial orientation of the wireless array 100 relative to a magneticfield. For example, the magnetometer 106 may be an integrated circuitthat is secured to the motherboard 108 of the wireless array 100 andthat is in signal communication with the controller 104 of the wirelessarray. A suitable magnetometer may be available from Honeywell Aerospacein Plymouth, Minn. as model designation HMC5883L. A suitablemagnetometer may also be available from Freescale Semiconductor, Inc. inAustin, Tex. as model designation MAG3110.

Knowing the spatial orientation of the wireless array 100 itselfprovides the ability to determine the orientation of the transceiversT1-T8 and their associated antennas 102 in the wireless array as well.As seen in FIG. 1, the transceivers T1-T8 and antennas 102 of thewireless array 100 are distributed around the circumference of thewireless array. The antennas 102 may be directional antennas configuredto broadcast wireless signals in a radial direction away from the centerof the wireless array. Accordingly, each antenna 102 in the wirelessarray, in this example, may broadcast a directional antenna pattern 110that covers a portion of the circular area surrounding the wirelessarray 100.

In the example shown, the antennas 102 of the wireless array 100 areposition at 45° intervals around the circumference of the wirelessarray. For example, transceiver T1 may be described as being 0° from thetop of the wireless array 100; transceiver T2 is 45° clockwise (CW) fromthe top of the wireless array; transceiver T3 is 90° CW; and so forthfor transceivers T4-T8.

The magnetometer 106 may indicate the spatial orientation of thewireless array 100 as an azimuth value corresponding to the angularmeasurement of the bearing of the wireless array relative to a referencebearing. The bearing of the wireless array 100 may be describedaccording to the orientation of the transceiver at the top of thewireless array, which is transceiver T1 in this example. A referencebearing corresponding to magnetic north may be used to determine thespatial orientation of the wireless array 100 relative to the surface ofthe Earth.

In this example, the reference bearing 112 corresponds to 0° as shown inFIG. 1. Accordingly, the spatial orientation of the wireless array 100may be described as 0° because the transceiver T1 at the top of thearray has a 0° orientation. If the transceiver T1 is oriented at 45° CWfrom the reference bearing 112 (i.e., 0°), then the orientation of thewireless array 100 may be described as 45°. When the spatial orientationof the wireless array 100 is known along with the positions of thetransceivers T1-T8 and the antennas 102 in the wireless array, thespatial orientation of the antennas may also be determined, i.e., whichdirection the antennas are pointing.

As mentioned above, the antennas 102 of the wireless array 100 arepositioned around the circumference of the wireless array in 45°intervals. Thus, the spatial orientation of an antenna 102 may bedetermined, in this example, by adding the spatial orientation of thewireless array 100 itself to the position of the antenna in the wirelessarray. For example, if the wireless array 100 is oriented 45° CW fromthe reference bearing 112 (i.e. 0°), each of the antennas 102 in thewireless array, in this example, is shifted 45° CW. Therefore when thewireless array 100, in this example, is oriented at 45°, transceiver T3is oriented at 135° (45° wireless array orientation plus 90° antennaposition equals 135° antenna orientation). The spatial orientation ofthe antennas 102 in the wireless array 100 may be used when determiningthe location of a station in a wireless environment as discussed furtherbelow.

One of the transceivers T1-T8 in the wireless array 100 may bedesignated as the monitor transceiver for the wireless array. Themonitor transceiver may be used to monitor other wireless arrays in thewireless environment that are in signal communication with the wirelessarray 100 having the monitor transceiver. In this example, the monitortransceiver is transceiver T1 as indicated in FIG. 1 with the heavieroutline. Where other wireless arrays also include multiple transceivers,the monitor transceiver T1 of the wireless array 100 may monitor theindividual transceivers of the other wireless arrays.

The wireless array 100 may also include network uplinks (not shown) toconnect the wireless array to a wired network. The network uplinks maybe, for example, Ethernet interfaces to connect the wireless array to awired IP-based (internet protocol) network. As discussed further below,the network uplinks may connect the wireless array 100 to a networkmanagement system for remote monitoring and management of the wirelessarray in the wireless environment.

Wireless Environments and Network Management Systems

Referring to FIG. 2, three wireless access points 114 a, 114 b, and 114c are shown installed in a wireless environment 116. In this example,the three wireless access points 114 a, 114 b, and 114 c are wirelessarrays. Each wireless array 114 in this example includes fourtransceivers—one monitoring transceiver and three non-monitoringtransceivers. The wireless arrays 114, in this example, serve aswireless access points for a station 118 in the wireless environment.The station 118 may be any device configured to transmit wirelesssignals according to a wireless protocol, e.g., the IEEE 802.11protocol. A station may be, for example: a desktop, laptop, tablet, orpalmtop computer; a wireless access point; a mobile telephone, awireless tag, and the like. In the example shown, the station 118 is acomputer. The wireless arrays 114, in the example shown, may also beconsidered stations as each wireless array may exchange wireless signalswith the other wireless arrays. Each of the wireless arrays 114 in thisexample is connected to a wired network 120. The wireless arrays 114provide the station 118 with access to the wired network 120 byexchanging wireless signals with the station.

Propagation of the wireless signals through the wireless environment 116may be affected by the unique physical properties of the wirelessenvironment. Attenuation of the wireless signals may result from freespace propagation, reflection, diffraction, and scattering. The level ofattenuation the wireless signals undergo may be referred to as pathloss, which represents the difference between the power of the wirelesssignal when the signal is transmitted and the power of the wirelesssignal when the signal is received. Path loss may be measured indecibels (dB).

Path loss may depend on, for example, the distance between the station118 and the wireless arrays 114 as well as the amount and type ofobstructions 122 present in the wireless environment 116. Obstructionsmay include, for example, walls, doors, windows, ceilings, floors,cubicles, desks, filing cabinets, tables, furniture, and even people. Itwill be thus understood that wireless signals may propagate throughvarious wireless environments differently due to the unique physicalproperties of each environment.

Various models exist to quantify the path loss (i.e., the amount ofattenuation) that is expected for a wireless environment 116. A pathloss model that quantifies the expected path loss (PL) in dB may beexpressed as:

PL=PL_(ref)+10 log(D ^(n))+S  (1)

where PL represents the difference between the transmitted signal powerand the received signal power; PL_(ref) represents a reference path lossin dB between the transmitted signal power and the received signal powerwhen the transmitter (i.e., the station 118) and receiver (i.e., awireless array 114) are around one meter apart with no obstructions inbetween; D represents the distance in meters between the transmitter andthe receiver; n represents a path loss exponent for the wirelessenvironment 116; and S represents a shadow fading factor.

The path loss exponent, n, in this example, may depend on the frequencyof the wireless signal, the type of wireless environment 116, and theobstructions present in the wireless environment. At 2.4 GHz(gigahertz), for example, the following path loss exponents may be used:n=2 open free space environments (e.g., outdoors); n=3-3.5 for indooroffice environments; and n=4-4.5 for indoor home or hospitalenvironments, which may be relatively more dense as a result of havingmore obstructions. The wireless environment 116 in FIG. 2, for example,includes two solid obstructions 122 that may affect propagation of thewireless signals through the environment and contribute to path loss.

The shadow fading factor, S, in this example path loss model, may alsodepend on the amount and type of obstructions 122 present in thewireless environment 116. Where there is a relatively high number ofobstructions 122 present in the wireless environment 116, a suitableshadow fading factor may be, for example, around 7 dB. As discussedfurther below, however, the accuracy of the path loss model may dependon using a shadow fading factor that accurately corresponds to theunique physical properties of the wireless environment 116.

Still referring to FIG. 2, the wired network 120 may also be in signalcommunication with a network management system 124. In turn, the networkmanagement system 124 may be in signal communication with the wirelessarrays 114 via the wired network 120 and in signal communication withthe station 118 in the wireless environment 116 via the wireless arrays.The network management system 124 may monitor and configure the wirelessarrays 114 installed in the wireless environment 116. The networkmanagement system 124 may also monitor wireless communications betweenthe wireless arrays 114 and the station 118 in the wireless environment116.

The network management system 124 includes various modules that localizethe station 118 in signal communication with the wireless arrays 114 inthe wireless environment 116. As discussed in more detail below, thenetwork management system 124 in this example includes: an interfacemodule 126 that receives user input corresponding to the locations ofthe wireless arrays 114 in the wireless environment 116; a shadow fadingdetermination module 128 that determines a shadow fading factor for thewireless environment; a distance determination module 130 thatdetermines the distance between the station 118 and the wireless arrays114; and a localization module 132 that determines an approximatelocation for the station 118 in the wireless environment.

The interface module 126 may display a scaled floor map of the wirelessenvironment 116. A user may indicate on the floor map the location ofone or more wireless arrays 114 installed in the wireless environment116. The location of a wireless array 114 may be received as user inputfrom the user and stored, for example, as an x-y coordinate.Additionally, because the floor map is scaled, the network managementsystem 124 may determine the distance between the wireless arrays 114installed in the wireless environment 116. The network management system124 may determine the distance between the coordinates for the wirelessarrays 114 on the floor map and scale the map distance to an actualdistance using the map scale. In the example shown, the networkmanagement system 124 may determine respective distances between thewireless arrays 114: distance 131 a between wireless array 114 a and 114b; distance 131 b between wireless array 114 a and 114 c; and distance131 c between wireless array 114 b and 114 c. As discussed furtherbelow, the respective distances 131 between the wireless arrays 114 inthe wireless environment 116 may be used to determine the location ofthe station 118 in the wireless environment.

The network management system 124 may determine the location of thestation 118 in the wireless environment 116 based on wireless signalsreceived at the wireless arrays 114 from the station. More particularly,the network management system 124 may determine the location of thestation 118 in the wireless environment 116 based on the power of thewireless signals received at wireless arrays 114 from the station.Determining the location of the station 118 in the wireless environmentmay be referred to as station localization.

The power of a received wireless signal may be referred to as thereceived signal strength (RSS). An example model for quantifying the RSSmay be expressed as:

Rx _(pwr) =Tx _(pwr) −L _(Tx) +G _(Tx) −PL−L _(Rx) +G _(Rx)  (2)

where Rx_(pwr) is the received signal strength (RSS) in dB; Tx_(pwr) isthe output power of the transmitter (i.e., the station 118) in dB;L_(Tx) is the sum of all cable and connector losses in dB at thetransmitter; G_(Tx) is the antenna gain at the transmitter in dBi(decibel isotropic); PL is the path loss of the wireless signal in dB;L_(Rx) is the sum of all cable and connector losses in dB at thereceiver (i.e., the wireless array 114); and G_(Rx) is the antenna gainat the receiver in dBi.

As mentioned above, the network management system 124 in this exampledetermines the location of the station 118 in the wireless environment116 based on wireless signals received at the wireless arrays 114 fromthe station. When the station 118 is in signal communication with thewireless arrays 114, the station may probe the transceivers T1-T8(FIG. 1) of the wireless arrays to determine which wireless array and,in particular, which wireless array transceiver is most suitable toassociate with (e.g., based on signal strength). The wireless arrays 114in this example include multiple transceivers T1-T8 as discussed above.Each transceiver T1-T8 may broadcast multiple SSIDs (service setidentifiers). Accordingly, the station 118, in this example, maytransmit a wireless signal as a probe request to each transceiver-SSIDcombination the station can detect in order to determine which wirelessarray 114, transceiver T1-T8, and SSID is most suitable to associatewith. In some example implementations, the station may automaticallydetermine which transceiver to associate with based on the signalstrength, e.g., the transceiver with the strongest signal strength.Additionally, selection of which SSID to connect to may be automaticbased on a pre-configuration of the station or may be manual based on auser selection.

The wireless arrays 114 may store the RSS for the probe requestsreceived from the station 118. It will be understood that, in somecircumstances, the station 118 may not transmit a probe request to atransceiver T1-T8 of a wireless array 114 if the station cannot detectan SSID broadcast from the transceiver. In an example scenario, however,the station 118 may transmit a respective probe request to each of thewireless array transceivers T1-T8 the station 118 can detect.

Because the network management system 124 in this example is in signalcommunication with the wireless arrays 114 in the wireless environment116, the network management system may access the stored RSS values forthe probe requests from the station 118. The network management system124 may receive the RSS values from the wireless arrays 114 via thewired network 120 in response to receipt at the wireless arrays of arequest for the RSS values from the network management system. Thenetwork management system 124 may use the respective RSS values receivedfrom the wireless arrays to respectively determine the distance betweenthe station 118 and the wireless arrays 114. As shown in FIG. 2, thestation 118 is a distance 133 a away from wireless array 114 a; adistance 133 b away from wireless array 114 b; and a distance 133 c awayfrom wireless array 114 c.

To determine the distances 133 between the station 118 and the wirelessarrays 114, the path loss model (1) may be substituted for the path lossparameter, PL, in the RSS model (2):

Rx _(pwr) =Tx _(pwr) −L _(Tx) +G _(Tx)−(PL _(ref)+10 log(D ^(n))+S)−L_(Rx) +G _(Rx)  (3)

The RSS model may then be rearranged to solve for the distanceparameter, D. Accordingly, the distance determination module 130 may usethe following rearranged RSS model to determine the distance between thestation 118 (i.e., the transmitter) and one of the wireless arrays 114(i.e., the receiver):

D= ^(n)√{square root over (antilog[(Tx _(pwr) −L _(Tx) +G _(Tx) −PL_(ref) −S−L _(Rx) −G _(Rx) −Rx _(pwr))/10])}  (4)

In this rearranged RSS model, the distance, D, is the unknown value, andthe values for Rx_(pwr), Tx_(pwr), L_(Tx), G_(Tx), L_(Rx), G_(Rx),PL_(ref) and S may be known. The power of the received signal, Rx_(pwr),is the RSS of the wireless signals received at the wireless array 114from the station 118. The wireless array 114 stores RSS values forwireless signals received from the station 118, and the networkmanagement system 124 may access the RSS values stored at the wirelessarrays. The power of the transmitted wireless signal, Tx_(pwr), is theoutput power of the station 118 (i.e., the transmitter). The value usedfor the power of the transmitted signal, Tx_(pwr), may be based on, forexample, the types of wireless components (e.g., antennas) found inwireless devices such as laptops or mobile telephones. For example, thevalue of the power of the transmitted wireless signal, Tx_(pwr), may bearound 13-18 dB. In some example implementations, a value of 15 dB maybe employed for the value of the power of the transmitted wirelesssignal, Tx_(pwr).

The loss values, L_(Tx) and L_(Rx), may be negligible since the station118 and the wireless arrays 114, in this example, use internal antennas,which results in negligible cable loss. Accordingly, the distancedetermination module 130 in this example assumes that L_(Tx) and L_(Rx)are equal to zero.

Like the value for the power of the transmitted wireless signal,Tx_(pwr), the values used for the antenna gain, G_(Tx) and G_(Rx), maybe based on the types of antennas found in wireless devices such aslaptops and mobile telephones. In some example implementations, thevalues for the antenna gain, G_(Tx) and G_(Rx), may be obtained from theantenna manufacturer or market data and may be around 0-1 dBi. In otherexample implementations, the values for the antenna gain, G_(Tx) andG_(Rx) may be around 0.5 dBi.

As mentioned above, the reference path loss, PL_(ref), may be areference value for the path loss observed when the station 118 and awireless array 114 are around one meter apart with no obstructions inbetween. The value for the reference path loss, PL_(ref), may bedetermined based on the wavelength of the wireless signal. For example,the following formulas may be used to determine a value for thereference path loss, PL_(ref):

$\begin{matrix}{20\mspace{14mu} {\log_{10}\left( \frac{4\pi}{\lambda} \right)}} & (5) \\{\lambda = \frac{c}{f}} & (6)\end{matrix}$

where λ is the wavelength of the wireless signal in meters (m) anddetermined by dividing the speed of light (299,792,458 meters persecond), c, by the frequency (cycles per second), f, of the wirelesssignal. In the field of wireless communications, different frequenciesmay define different channels. For example, under the IEEE 802.11standard, channel 1 has a frequency of 2.412 GHz, channel 11 has afrequency of 2.462 GHz, etc. Accordingly, a wireless signal transmittedat a frequency of 2.412 GHz has a wavelength, λ, of around 0.124 m.

Also mentioned above, the shadow fading factor, S, may depend on thetype of wireless environment 116 and the obstructions 122 present in thewireless environment. The shadow fading observed at the wirelessenvironment 116, however, may vary significantly depending on the uniquephysical properties of the wireless environment such as, for example,the amount and type of obstructions 122 present in the wirelessenvironment. Accordingly, the accuracy of the distance calculation maydepend on an accurate value for the shadow fading factor. Therefore, theaccuracy of the distance formula may be advantageously improved by usinga shadow fading factor that accurately corresponds to the shadow fadingactually observed in the wireless environment 116.

The network management system 124 in this example includes a shadowfading determination module 128 that determines a shadow fading factorfor the wireless environment 116. The shadow fading determination module128 uses a technique similar to determining the distance between thestation 118 and a wireless array in the wireless environment 116. Asmentioned above, the wireless arrays 114 include a monitor transceiver(e.g., transceiver T1) to monitor the other wireless arrays in thewireless environment 116. The monitor transceiver T1 of a wireless array114 exchanges wireless signals with the other wireless arrays in thewireless environment. Each wireless array 114 in the wirelessenvironment 116 may monitor the other wireless arrays by exchangingwireless signals in this fashion.

Additionally, the wireless arrays 114 may store RSS values for wirelesssignals received from the other wireless arrays in the wirelessenvironment 116. Furthermore, the respective distances 131 between thewireless arrays 114 in the wireless environment 116 may be known as aresult of the user input received indicating the respective positions ofthe wireless arrays on the floor map for the wireless environment.

To determine the shadow fading factor for the wireless environment 116,the path loss model (1) may again be substituted for the path lossparameter, PL, in the RSS model (2) to obtain the model according toequation 3 above. The RSS model may again be rearranged to solve for S:

S=Tx _(pwr) −L _(Tx) +G _(Tx) −PL _(ref)−10 log(D ^(n))+G _(Rx) −L _(Rx)−Rx _(pwr)  (7)

In this example, the distance, D, between the transmitter (i.e., one ofthe wireless arrays) and the receiver (i.e., another one of the wirelessarrays) is known based on the respective positions for the wirelessarrays 114 indicated on the floor map for the wireless environment 116.Accordingly, the known values for the rearranged RSS model may be usedto determine a shadow fading factor, S.

Because the wireless environment 116 may include more than one wirelessarray 114, the shadow fading determination module 128 may determinemultiple shadow fading factors, S, and determine an average shadowfading factor, S_(avg), based on the multiple shadow fading factors. Theshadow fading determination module 128 may determine a shadow fadingfactor, S, for each pairing of a monitor transceiver 115 at one wirelessarray and a non-monitor transceiver 117 at another wireless array. Asmentioned above, the monitor transceiver of a wireless array may monitorthe non-monitor transceivers of another wireless array.

When determining multiple shadow fading factors, S, the shadow fadingdetermination module 128 may pair each respective monitor transceiver115 a, 115 b, and 115 c in the wireless arrays 114 a, 114 b, and 114 cwith the respective non-monitor transceivers 117 a, 117 b, and 117 c ofthe corresponding wireless arrays. In the example shown in FIG. 2, theshadow fading determination module 128 may pair the monitor transceiver115 a in wireless array 114 a with each of the respective threenon-monitor transceivers 117 b and 117 c of wireless arrays 114 b and114 c, which results in six transceiver pairings for the monitortransceiver 115 a of wireless array 114 a. The shadow fadingdetermination module 128 may make similar transceiver pairings for therespective monitor radios 115 b and 115 c in wireless arrays 114 b and114 c for a total of eighteen transceiver pairings in this example.Accordingly, the shadow fading determination module 128 may determineand average a total eighteen shadow fading factors, S, to calculate theaverage shadow fading factor, S_(avg), for the wireless environment 116.As another example, where three wireless arrays in a wirelessenvironment each include eight total transceivers (one monitoring andseven non-monitoring transceivers) as in FIG. 1, the shadow fadingdetermination module 128 may determine and average a total of forty-twoshadow fading factors, S, to calculate the average shadow fading factor,S_(avg), for the wireless environment.

The distance determination module 130 of the network management system124 may then, when determining the respective distances 133 between thestation 118 and a wireless array 114, use the average shadow fadingfactor, S_(avg), instead of a shadow fading factor typical to the typeof wireless environment. In this way, the accuracy of the distancedetermination may be advantageously improved.

The network management system 124 in the example shown also includes alocalization module 132 that determines the location of the station 118in the wireless environment. The techniques used to localize the station118 may differ depending on the number of wireless arrays 114 that areinstalled in the wireless environment 116. As discussed in more detailbelow, the localization module 132 of the network management system 124may employ one technique when three or more arrays 114 are installed inthe wireless environment 116 and a different technique when there aretwo wireless arrays installed.

Referring to FIG. 3, a flow chart 134 of example method steps fordetermining an average shadow fading factor for a wireless environmentis shown. A network management system 124 (FIG. 2) may carry out theexample method steps shown in FIG. 3. The network management system 124may be a network management system as described above in reference toFIG. 2. The interface module 126 of the network management system 124may display a map of the wireless environment 116 having the wirelessarrays 114 (step 136). The map may be a floor map and indicate theposition of physical structures (e.g., walls, etc.) in the wirelessenvironment 116. The map may include a map scale such that a distance onthe map may be scaled to an actual distance in the wireless environment116. The interface module 126 may receive user input relating to thelocation of the wireless arrays 114 in the wireless environment 116(step 138). For example, a user may indicate on the map the locationsthat correspond to the installation locations for the wireless array 114in the wireless environment 116. The network management system 124 maydetermine the respective distances 131 between the wireless arrays 114based on the respective positions for the wireless arrays 114 indicatedon the map (step 140). The map scale may be used to scale the mapdistances 131 to actual distances between the wireless arrays 114 in thewireless environment 116.

The shadow fading determination module 128 then selects a transceiverpairing from the transceivers of the group of wireless arrays 114installed in the wireless environment 116 (step 142). As discussedabove, a monitor transceiver 115 (e.g., transceiver T1) at each wirelessarray 114 may monitor the non-monitor transceivers 117 of the otherwireless arrays in the wireless environment 116 by exchanging wirelesssignals with the non-monitor transceivers of the other wireless arrays.The wireless arrays 114 may store RSS information relating to thewireless signals exchanged between the monitor transceivers 115 and thenon-monitor transceivers 117. The network management system 124 mayquery a wireless array 114 having a monitor transceiver for the RSSinformation relating to wireless signals exchanged between the monitortransceiver and a non-monitor transceiver of the another wireless array(step 144), and the RSS information for the transceiver pairing may bereceived at the network management system from the wireless array inresponse (step 146).

Based on the RSS information for the transceiver pairing, the shadowfading determination module 128 may determine a shadow fading factor forthe wireless environment 116 (step 148). The shadow fading determinationmodule 128 may determine a shadow fading factor for each transceiverpairing as discussed above in reference to FIG. 2. If there areadditional transceiver pairings (step 150), then the shadow fadingfactor determination module 128 may select a new transceiver pairing(step 142) and determine additional signal fading factors for the newtransceiver pairing (steps 144-148). In some example implementations,the shadow fading determination module 128 may determine signal fadingfactors for every transceiver pairing. If multiple signal fadingfactors, S, are determined, then the shadow fading determination module128 may determine an average signal fading factor, S_(avg), for thewireless environment 116 by averaging the multiple signal fading factors(step 152). As discussed above, the distance determination module 130may use the average signal fading factor, S_(avg), when determining thedistance between a station 118 and a wireless array 114 in the wirelessenvironment 116 in order to improve the accuracy of the distancedetermination.

Station Localization Using Three or More Wireless Arrays

Referring to FIG. 4, a wireless environment 116 having three wirelessaccess points 114 a, 114 b, and 114 c is shown. In this example, thethree wireless access points 114 a, 114 b, and 114 c are wirelessarrays. When the wireless environment 116 includes three or morewireless arrays 114, the localization module 132 (FIG. 1) may employlateration approach to determine the location of the station 118 in thewireless environment. When the wireless environment 116 includes threewireless arrays 114 as shown by way of example in FIG. 4, the laterationapproach may be referred to as trilateration; when the wirelessenvironment includes more than three wireless arrays, the laterationapproach may be referred to as multilateration.

As discussed above in reference to FIG. 2, the location of the wirelessarrays 114 in the wireless environment 116 may be indicated on a scaledfloor map of the wireless environment. Therefore, the respectivedistances 131 between the wireless arrays may be known to the networkmanagement system 124. The station 118 between the wireless arrays 114may transmit wireless signals as probe requests to the wireless arrays,and the wireless arrays may store respective RSS values for the proberequests. Additionally, the wireless arrays 114 may exchange wirelesssignals with each other as each wireless array monitors the otherwireless arrays in the wireless environment 116 via a monitortransceiver (e.g., transceiver T1). The wireless arrays 114 may alsostore RSS values for the wireless signals received from the otherwireless arrays. The network management system 124 may query thewireless arrays 114 for the RSS values corresponding to wireless signalsfrom the station and from the other wireless arrays and receive the RSSinformation from the wireless arrays in response.

Once the network management system 124 has obtained the RSS information,the shadow fading determination module 128 may first determine anaverage shadow fading factor, S_(avg), for the wireless environment 116according to the approach set forth above, i.e., based on the knowndistances 131 between the wireless arrays 114 and the RSS values of thewireless signals exchanged between the wireless arrays. The distancedetermination module 130 of the network management system 124 may thendetermine the respective distances 133 between the station 118 and thewireless arrays 114 according to the approach set forth above, i.e.,based on the RSS values of the wireless signals received from thestation and the average shadow fading factor, S_(avg), for the wirelessenvironment 116.

In this example approach, the direction of the station 118 relative tothe wireless arrays 114 may be unknown. For example, if the distancedetermination module 130 determines that the station 118 is 20 feet awayfrom a wireless array 114, the station may be 20 feet away in anydirection, i.e., 20 feet north of the wireless array, 20 feet south, 20feet east, 20 feet west, etc. As a result, the distance determinationmodule 130 identifies a circular region having a radius equal to thedistance between the station 118 and the wireless array 114. Thecircular region thus represents all possible directions the station 118may be located at relative to the wireless array 114. As seen in FIG. 4,circular regions 154 a, 154 b, and 154 c have been respectivelydetermined for each of the wireless arrays 114 a, 114 b, and 114 c. Asshown by way of example in FIG. 4, each wireless array 114 is at thecenter of its respective circular region 154. Additionally, the radii156 the circular regions 154 correspond to the respective distances 133between the station 118 and the wireless arrays 114 in FIG. 2. As seenin FIG. 4, the radius 156 a of circular region 154 a corresponds to thedistance 133 a between the station 118 and wireless array 114 a; theradius 156 b of circular region 154 b corresponds to the distance 133 bbetween the station 118 and wireless array 114 b; and the radius 156 cof circular region 154 c corresponds to the distance 133 c between thestation 118 and wireless array 114 c.

As seen in FIG. 4, the three circular regions 154, in this example,intersect resulting in region 158 where the three circular regionsoverlap. The localization module 132, in this example, identifies theoverlapping region 158 as a sub-region in the wireless environment thatthe station 118 is located in. To approximate the location of thestation 118 in the overlapping region 158, the localization moduledetermines the center 160 of the overlapping region 158. Thelocalization module 132 may determine the center 160 of the overlappingregion 158 using trilateration techniques. The localization module 132may thus determine that the center 160 of the overlapping region 158corresponds to the approximate location of the station 118 in thewireless environment.

This approach may be extended where more than three wireless arrays 114are installed in the wireless environment, in which case thelocalization module 132 may employ multilateration techniques tolocalize the station 118. Where the wireless environment includes morethan three wireless arrays 114, the localization module 130 may narrowdown the location of the station 118 to a relatively smaller overlappingregion 158, and, as a result, the approximate location of the stationmay be more accurate.

Referring to FIG. 5, a flowchart 162 of example method steps fordetermining the location of a station 118 in a wireless environment 116having three or more wireless access points 114 (e.g., wireless arrays)is shown. A network management system 124 (FIG. 2) may also carry outthe example method steps shown in FIG. 5. The network management system124 may be a network management system as described above in referenceto FIG. 2. A shadow fading determination module 128 may determine anaverage signal fading factor, S_(avg), for the wireless environment 116(step 164) according to the approach set forth above. Also discussedabove, a station 118 in the wireless environment 116 may transmitwireless signals to the wireless arrays 114, and the wireless arrays maydetermine and store RSS information relating to the wireless signalsreceived from the station. The network management system 124 may querythe wireless arrays 114 for the RSS information relating to the wirelesssignals received at the wireless arrays from the station (step 166), andthe RSS information may be received at the network management systemfrom the wireless arrays in response (step 168).

The distance determination module 130 may determine the distance betweenthe station 118 and a wireless array 114 based on the RSS informationreceived from the wireless array (step 170). As mentioned above, thedistance determination module 130 may use the average shadow fadingfactor, S_(avg), when determining the distance 133 between the station118 and the wireless array 114 to improve the accuracy of the distancedetermination. In turn, the localization module 132 may identify acircular region 154 associated with the wireless array 114 based on thedistance between the station and the wireless array (step 172). In thisexample, the radius 156 for the circular region 154 associated with thewireless array 114 may be equal to the distance 133 between the station118 and the wireless array. Additionally, the circular region 154 may beconfigured such that the wireless array 114 associated with the circularregion 154 is at the center of the circular region. If there areadditional wireless arrays 114 in the wireless environment (step 174),then steps 170-172 may be repeated to determine respective circularregions 154 for the additional wireless arrays. In this exampleapproach, three or more wireless arrays are used to determine thelocation of the station 118 in the wireless environment 116.

Once the localization module 132 determines the circular regions 154 forthe wireless arrays 114, the localization module identifies anoverlapping region 158 where the circular regions intersect (step 176),and determines the center 160 of the overlapping region (step 178). Asdiscussed above the localization module 132 may employ trilateration ormultilateration techniques to determine the center 160 of theoverlapping region 158. In this example, the localization module 132identifies the center 160 of the overlapping region 158 as correspondingto the approximate location of the station 118 in the wirelessenvironment 116 (step 180).

Station Localization Using Two Wireless Arrays

Referring now to FIG. 6A and FIG. 6B, a wireless environment 116 havingtwo wireless access points 114 a and 114 b and a station 118 is shown.In this example, the wireless environment 116 may be an outdoor wirelessenvironment, and the wireless access points 114 a and 114 b are wirelessarrays having multiple transceivers T1-T4. When a wireless environment116 includes two wireless arrays 114, the localization module 132 (FIG.2) of the network management system 124 may employ an alternativeapproach to determine the location of the station 118 in the wirelessenvironment. In this example alternative approach, the localizationmodule 132 uses the orientation information provided by the magnetometer106 (FIG. 1) of each wireless array 114 when localizing the station 118in the wireless environment 116. Instead of using circular regions andlateration as described above, the localization module 132 in thisexample approach identifies multiple triangular sub-regions 182 (FIG.6B) in the wireless environment 116 and determines that the station islocated in one of the triangular sub-regions of the wireless environment116. The triangular sub-regions 182 are based on a set of coordinates184 a-h in the wireless environment 116. Each vertex of a triangularsub-region 182 corresponds to one of the coordinates. The localizationmodule 132, in this example, selects the coordinates 184 based on therespective orientations of the transceivers T1-T4 of the wireless arrays114 a and 114 b and based on the respective distances 186 a-h betweenthe station 118 and the transceivers of the wireless arrays.

As discussed above, the station 118 transmits wireless signals as proberequests to the transceivers T1-T4 of the wireless arrays 114, and thewireless arrays determine an RSS value for the wireless signals receivedat the transceivers. The transceivers T1-T4 of the wireless arrays 114may include directional antennas 102 (FIG. 1) that broadcast adirectional antenna pattern 110 as also discussed above. Furthermore,the magnetometer 106 indicates the orientation of the wireless array114, and the orientation information may be used to determine respectivespatial orientations of the wireless array transceivers T1-T4 (e.g., 0°,45°, 90°, etc.). The network management system 124 being in signalcommunication with the wireless arrays 114 and may retrieve theorientation information and the RSS values stored at the wirelessarrays.

The shadow fading determination module 128 may determine an averageshadow fading factor, S_(avg), for the wireless environment 116according to the approach set forth above. The distance determinationmodule 130 may use the average shadow fading factor, S_(avg), whendetermining the distance, D, between the station 118 and a wirelessarray transceiver T also according to the approach set forth above. Thelocalization module 132 then selects a coordinate 184 to associate witha wireless array transceiver T based on the distance, D, and based onthe spatial orientation of the wireless array transceiver (e.g., 0°,45°, 90°, etc.).

As seen in FIG. 6A, the station 118, in this example, is positionedbetween the two wireless arrays 114 a and 114 b in the wirelessenvironment 116. The two wireless arrays 114 a and 114 b in the exampleshown each include four transceivers T1-T4. The four transceivers T1-T4of each wireless array 114 a and 114 b are respectively oriented at 45°,135°, 225°, and 315° respectively (i.e., north-east, south-east,south-west, and north-west). The magnetometer 106 at each wireless array114 may provide information regarding the orientation of each wirelessarray, which may be used to determine the orientation of thetransceivers T1-T4. The network management system 124, in this example,may query the wireless arrays 114 for the orientation information anddetermine the respective orientations for the transceivers T1-T4 at eachwireless array. The distance determination module 130 of the networkmanagement system 124 may determine the respective distances between thestation 118 and the transceivers T1-T4 based on the RSS of wirelesssignals transmitted from the station to the wireless array transceivers.

Once the network management system 124 has determined respectivedistances 186 a-h between the station 118 and the transceivers T1-T4 aswell as the orientation of the transceivers, the localization module 132may identify a respective coordinate for the transceivers T1-T4. Thelocation of the coordinates, in this example, respectively correspond tothe orientation of the transceivers T1-T4 and respectively correspond tothe distance between the station 118 and the transceivers.

As shown in FIG. 6A, the localization module 132 has selected arespective coordinate for each transceiver T1-T4 at each wireless array114 a and 114 b. Accordingly, the localization module 132 has selectedeight total coordinates 184 a-h (four coordinates for the fourtransceivers of each wireless array). As seen in FIG. 6A, the positionfor the coordinates 184 respectively correspond to the orientations ofthe transceivers T1-T4 the coordinates are respectively associated with.Regarding wireless array 114 a, for example, transceiver T1 and itsassociated coordinate 184 a are both oriented north-west (315°) relativeto the wireless array. Additionally, the position of coordinate 184 arelative to transceiver T1 of wireless array 114 a corresponds thedetermined distance 186 a between the station 118 and transceivers T1.The distances 186 a-h between the station 118 and the transceivers T1-T4for the wireless arrays 114 a and 114 b may be determined based on theRSS of wireless signals transmitted to the transceivers from thestation.

Once the localization module 132 determines the set of coordinates 184,the localization module iteratively selects three of the coordinatesfrom the set of coordinates to form a triangular sub-region 182. In thisexample, the localization module 132 iteratively selects a threecoordinates 184 from the set of coordinates to form every possibletriangular sub-region 182 that could be formed from the set ofcoordinates. For each triangular sub-region 182 formed, the localizationmodule 132 determines the area of the triangular sub-region. Thelocalization module 132 then compares the areas of the triangularsub-regions to determine which triangular sub-region has the smallestarea.

In this example, the localization module 132 determines that the station118 is located in the triangular sub-region 182 having the smallestarea. To approximate the location of the station 118 in the triangularsub-region 182 having the smallest area, the localization module 132determines the circumcenter of the triangular sub-region. In thisexample, the circumcenter is the center of a circle that that passesthrough each vertex of the triangular sub-region (or alternatively, thecircumcenter is the intersection point of the perpendicular bisectors ofthe triangular sub-region). The localization module identifies thecircumcenter of the triangular sub-region having the smallest area asthe approximate location of the station in the wireless environment.

Referring to FIG. 6B, the potential triangular sub-regions 182 that maybe formed using the set of coordinates 184 of FIG. 6A is shown. As seenin FIG. 6B, the triangular sub-region 182 having the smallest area isthe triangular sub-region 182 a with vertices corresponding tocoordinates 184 d, 184 e, and 184 f. The localization module 132 maydetermine the circumcenter for this triangular sub-region 182 a andidentify the circumcenter as corresponding to the approximate locationof the station in the wireless environment 116.

Referring now to FIG. 7, a flowchart 188 of example method steps fordetermining the location of a station 118 having two wireless arrays 114is shown. Like before, a network management system 124 (FIG. 2) maycarry out the example method steps shown in FIG. 7. The networkmanagement system 124 may be a network management system as describedabove in reference to FIG. 2. Also, as previously shown, a shadow fadingdetermination module 128 may determine an average shadow fading factor,S_(avg), for the wireless environment 116 (step 190). As discussedabove, the wireless arrays 114, in this example, include a magnetometer106 that provides orientation information relating to the orientation ofthe wireless array, i.e., the direction the wireless array is facing.Accordingly, the network management system 124 may query the wirelessarrays 114 for the respective orientation information provided by themagnetometers 106 (step 192), and the orientation information may bereceived from the wireless arrays in response (step 194). Based on theorientation information, the network management system 124 may determinethe orientation of the transceivers of the wireless arrays 114 (step196).

Also discussed above, the station 118 may transmit wireless signals tothe wireless arrays 114 in the wireless environment 116, and thewireless arrays may store RSS information relating to the wirelesssignals received from the station. The network management system 124 mayquery the wireless arrays 114 for the station RSS information (step198), and the RSS information may be received from the wireless arraysin response (step 200). Based on the RSS information, the distancedetermination module 130 may determine the distance between the stationand a transceiver of a wireless array 114 (step 202). The localizationmodule 132 may then select a coordinate 184 in the wireless environment116 associated with the transceiver (step 204). The coordinate 184, inthis example, is selected such that the location of the coordinate 184corresponds to the distance between the station and the transceiver aswell as the spatial orientation of the transceiver. In this example, thelocalization module 132 selects the coordinate 184 such that theorientation of the coordinate in the wireless environment 116 relativeto the wireless array is the same as the spatial orientation for thetransceiver the coordinate is associated with. If there are additionaltransceivers (step 206), then the steps 202-204 may be repeated, in thisexample, to select additional coordinates 184 for the additionaltransceivers in signal communication with the station 118.

Once the localization module 132 has compiled a set of coordinates 184respectively corresponding to the transceivers in signal communicationwith the station 118, the localization module may select threecoordinates from the set of coordinates to identify a triangularsub-region 182 of the wireless environment 116 (step 208), andcalculates the area of the triangular sub-region (210). In this example,the localization module identifies every possible triangular sub-region182 that may be formed by selecting three coordinates 184 from the setof coordinates. Accordingly, the localization module 132 may repeatsteps 208-210 if there are additional triangular sub-regions 182 (step212) that may be formed by selecting three coordinates 184 from the setof coordinates.

The localization module 132, in this example, determines whichtriangular sub-region 182 has the smallest area and identifies thetriangular sub-region having the smallest area as the sub-region in thewireless environment 116 that the station is located in (step 214). Thelocalization module 132 then determines the circumcenter of thetriangular sub-region 182 having the smallest area (step 216) andidentifies the circumcenter as corresponding to the approximate locationof the station 118 in the wireless environment 116 (step 218). Thisapproach may be employed where there are two wireless arrays installedin the wireless environment 116.

It will be understood and appreciated that one or more of the processes,sub-processes, and process steps described in connection with FIGS. 1-7may be performed by hardware, software, or a combination of hardware andsoftware on one or more electronic or digitally-controlled devices. Thesoftware may reside in a software memory (not shown) in a suitableelectronic processing component or system such as, for example, one ormore of the functional systems, devices, components, modules, orsub-modules schematically depicted in FIG. 1. The software memory mayinclude an ordered listing of executable instructions for implementinglogical functions (that is, “logic” that may be implemented in digitalform such as digital circuitry or source code, or in analog form such asanalog source such as an analog electrical, sound, or video signal). Theinstructions may be executed within a processing module, which includes,for example, one or more microprocessors, general purpose processors,combinations of processors, digital signal processors (DSPs), fieldprogrammable gate arrays (FPGAs), or application-specific integratedcircuits (ASICs). Further, the schematic diagrams describe a logicaldivision of functions having physical (hardware and/or software)implementations that are not limited by architecture or the physicallayout of the functions. The example systems described in thisapplication may be implemented in a variety of configurations andoperate as hardware/software components in a single hardware/softwareunit, or in separate hardware/software units.

The executable instructions may be implemented as a computer programproduct having instructions stored therein which, when executed by aprocessing module of an electronic system (e.g., a wireless array inFIG. 1 and a network management system in FIG. 2), direct the electronicsystem to carry out the instructions. The computer program product maybe selectively embodied in any non-transitory computer-readable storagemedium for use by or in connection with an instruction execution system,apparatus, or device, such as a electronic computer-based system,processor-containing system, or other system that may selectively fetchthe instructions from the instruction execution system, apparatus, ordevice and execute the instructions. In the context of this document,computer-readable storage medium is any non-transitory means that maystore the program for use by or in connection with the instructionexecution system, apparatus, or device. The non-transitorycomputer-readable storage medium may selectively be, for example, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device. A non-exhaustive list ofmore specific examples of non-transitory computer readable mediainclude: an electrical connection having one or more wires (electronic);a portable computer diskette (magnetic); a random access memory(electronic); a read-only memory (electronic); an erasable programmableread only memory such as, for example, Flash memory (electronic); acompact disc memory such as, for example, CD-ROM, CD-R, CD-RW (optical);and digital versatile disc memory, i.e., DVD (optical). Note that thenon-transitory computer-readable storage medium may even be paper oranother suitable medium upon which the program is printed, as theprogram can be electronically captured via, for instance, opticalscanning of the paper or other medium, then compiled, interpreted, orotherwise processed in a suitable manner if necessary, and then storedin a computer memory or machine memory.

It will also be understood that the term “in signal communication” asused in this document means that two or more systems, devices,components, modules, or sub-modules are capable of communicating witheach other via signals that travel over some type of signal path. Thesignals may be communication, power, data, or energy signals, which maycommunicate information, power, or energy from a first system, device,component, module, or sub-module to a second system, device, component,module, or sub-module along a signal path between the first and secondsystem, device, component, module, or sub-module. The signal paths mayinclude physical, electrical, magnetic, electromagnetic,electrochemical, optical, wired, or wireless connections. The signalpaths may also include additional systems, devices, components, modules,or sub-modules between the first and second system, device, component,module, or sub-module.

The foregoing description of implementations has been presented forpurposes of illustration and description. It is not exhaustive and doesnot limit the claimed inventions to the precise form disclosed.Modifications and variations are possible in light of the abovedescription or may be acquired from practicing the invention. The claimsand their equivalents define the scope of the invention.

What is claimed is:
 1. A computer-implemented method of quantifying theshadow fading observed in a wireless environment having a plurality ofwireless access points comprising: receiving location informationrelating to respective locations of the plurality of wireless accesspoints at the wireless environment; determining a distance between thepair of wireless access points based on the location information; anddetermining a shadow fading factor based on the distance between thepair of wireless access points and based on received signal strength(RSS) information received from one of the wireless access points in thepair of wireless access points.
 2. The computer-implemented method ofclaim 1 wherein: the RSS information relates to a signal strength of atleast one wireless signal transmitted between the pair of wirelessaccess points; and the shadow fading factor is determined using a pathloss model and an RSS model.
 3. The computer-implemented method of claim2 wherein: the path loss model is expressed as PL=PL_(ref)+10log(D^(n))+S; and the RSS model is expressed asRx_(pwr)=Tx_(pwr)−L_(Tx)+G_(Tx)−PL−L_(Rx)+G_(Rx).
 4. Thecomputer-implemented method of claim 2 further comprising: selecting aplurality of transceiver pairings from the plurality of wireless accesspoints; determining a distance between individual wireless access pointsassociated with the transceiver pairings to obtain a plurality ofdistances; determining a plurality of shadow fading factors based on theplurality of distances and RSS information respectively associated withthe plurality of transceiver pairings; and determining an average shadowfading factor based on the plurality of shadow fading factors.
 5. Thecomputer-implemented method of claim 2 further comprising: displaying amap of the wireless environment; and receiving the location informationas user input wherein the user input relates to positions on the map andwherein the positions on the map correspond to the respective locationsof the plurality of wireless access points at the wireless environment.6. A system for quantifying the shadow fading observed in a wirelessenvironment having a plurality of wireless access points comprising: adistance determination module in signal communication with the pluralityof wireless access points, the distance determination module determinesa distance between a pair of wireless access points in the plurality ofwireless access points based on location information that relates torespective locations of the plurality of wireless access points at thewireless environment; and a shadow fading determination module in signalcommunication with the plurality of wireless access points, the shadowfading determination module determines a shadow fading factor based onthe distance between the pair of wireless access points and based onreceived signal strength (RSS) information received from one of thewireless access points of the pair of wireless access points.
 7. Thesystem of claim 6 wherein: the RSS information relates to a signalstrength of at least one wireless signal transmitted between the pair ofwireless access points; and the shadow fading determination moduledetermines the shadow fading factor using a path loss model and an RSSmodel.
 8. The system of claim 7 wherein: the path loss model isexpressed as PL=PL_(ref)+10 log(D^(n))+S; and the RSS model is expressedas Rx_(pwr)=Tx_(pwr)−L_(Tx)+G_(Tx)−PL−L_(Rx)+G_(Rx).
 9. The system ofclaim 7 wherein: the distance determination module selects a pluralityof transceiver pairings from the plurality of wireless access points;the distance determination module determines a distance betweenindividual wireless access points associated with the transceiverpairings to obtain a plurality of distances; the shadow fadingdetermination module determines a plurality of shadow fading factorsbased on the plurality of distances and RSS information respectivelyassociated with the transceiver pairings; and the shadow fadingdetermination module determines an average shadow fading factor based onthe plurality of shadow fading factors.
 10. The system of claim 7further comprising an interface module that displays a map of thewireless environment and receives the location information as user inputwherein the user input relates to positions on the map and wherein thepositions on the map correspond to the respective locations of theplurality of wireless access points at the wireless environment.
 11. Acomputer-implemented method of localizing a station in a wirelessenvironment having a plurality of wireless access points comprising:determining a shadow fading factor for the wireless environment;determining a plurality of distances between the station and individualwireless access points in the plurality of wireless access points basedon the shadow fading factor for the wireless environment and based onreceived signal strength (RSS) information received from the individualwireless access points; identifying a sub-region in the wirelessenvironment that the station is located in based on the plurality ofdistances; and identifying a location associated with the sub-regionthat corresponds to an approximate location of the station at thewireless environment.
 12. The computer-implemented method of claim 11wherein: the RSS information relates to signal strengths of at least onewireless signal respectively transmitted between the station and theindividual wireless access points, and individual distances in theplurality of distances are determined using a path loss model and an RSSmodel.
 13. The computer-implemented method of claim 12 wherein: the pathloss model is expressed as PL=PL_(ref)+10 log(D^(n))+S; and the RSSmodel is expressed as Rx_(pwr)=Tx_(pwr)−L_(Tx)+G_(Tx)−PL−L_(Rx)+G_(Rx).14. The computer-implemented method of claim 12 wherein: the group ofwireless access points includes at least three wireless access points;identifying a sub-region in the wireless environment that the station islocated in includes identifying respective circular regions for theindividual wireless access points wherein respective radii of thecircular regions respectively correspond to the individual distances inthe plurality of distances and wherein centers of the circular regionsrespectively correspond to locations of the individual wireless accesspoints at the wireless environment, identifying an overlapping regioncorresponding to an intersection of the circular regions; andidentifying a location associated with the sub-region that correspondsto an approximate location of the station in the wireless environmentincludes determining a center of the overlapping region, and identifyingthe center of the overlapping region as the location that corresponds tothe approximate location of the station at the wireless environment. 15.The computer-implemented method of claim 12 wherein: the group ofwireless access points includes two wireless access points, the wirelessaccess points each having a plurality of transceivers and a magnetometerthat determines a spatial orientation of the wireless access point; theplurality of distances between the station and the individual wirelessaccess points includes distances between the station and individualtransceivers in the plurality of transceivers; and identifying asub-region in the wireless environment that the station is located inincludes identifying a plurality of triangular sub-regions of thewireless environment based on respective spatial orientations of theindividual transceivers and the respective distances between the stationand the individual transceivers, and determining that one of thetriangular sub-regions in the plurality of triangular sub-regions is thesub-region in the wireless environment that the station is located in.16. The computer-implemented method of claim 15 wherein: individualtriangular sub-regions in the plurality of triangular sub-regions havevertices corresponding to a set of three coordinates in the wirelessenvironment; and individual coordinates in the set of coordinatescorrespond to a spatial orientation of one of the transceivers and adistance between the station and the transceiver.
 17. Thecomputer-implemented method of claim 15 wherein: determining that one ofthe triangular sub-regions in the plurality of triangular sub-regions isthe sub-region in the wireless environment that the station is locatedin includes determining respective areas for individual triangularsub-regions in the plurality of triangular sub-regions, identifying atriangular sub-region in the plurality of triangular sub-regions havingthe smallest area, and determining that the triangular sub-region havingthe smallest area is the triangular sub-region the station is locatedin.
 18. The computer-implemented method of claim 17 wherein identifyinga location associated with the sub-region that corresponds to anapproximate location of the station in the wireless environmentincludes: determining a center of the triangular sub-region the stationis located in; and identifying the center of the triangular sub-regionthe station is located in as the location that corresponds to theapproximate location of the station in the wireless environment.
 19. Thecomputer-implemented method of claim 18 wherein the center of thetriangular sub-region the station is located in is the circumcenter. 20.The computer-implemented method of claim 15 further comprisingdetermining the respective spatial orientations of the individualtransceivers in the individual wireless arrays based on orientationinformation received from the individual wireless arrays.
 21. A systemfor localizing a station in a wireless environment having a plurality ofwireless access points comprising: a shadow fading determination modulethat determines a shadow fading factor for the wireless environment; adistance determination module that determines a plurality of distancesbetween the station and individual wireless access points in theplurality of wireless access points based on the shadow fading factorfor the wireless environment and based on received signal strength (RSS)information received from individual wireless access points in theplurality of access points; and a localization module that identifies asub-region in the wireless environment that the station is located inbased on the plurality of distances and identifies a location associatedwith the sub-region that corresponds to an approximate location of thestation at the wireless environment.
 22. The system of claim 21 wherein:the RSS information relates to signal strengths of at least one wirelesssignal respectively transmitted between the station and the individualwireless access points, and individual distances in the plurality ofdistances are determined using a path loss model and an RSS model. 23.The system of claim 22 wherein: the path loss model is expressed asPL=PL_(ref)+10 log(D^(n))+S; and the RSS model is expressed asRx_(pwr)=Tx_(pwr)−L_(Tx)+G_(Tx)−PL−L_(Rx)+G_(Rx).
 24. The system ofclaim 22 wherein: the group of wireless access points includes at leastthree wireless access points; the localization module identifiesrespective circular regions for the individual wireless access pointswherein respective radii of the circular regions respectively correspondto the distances between the station and the individual wireless accesspoints and wherein respective centers of the circular regionsrespectively correspond to locations of the individual wireless accesspoints at the wireless environment; the localization module identifiesan overlapping region corresponding to an intersection of the circularregions; the localization module determines a center of the overlappingregion, and the localization module identifies the center of theoverlapping region as the location that corresponds to the approximatelocation of the station in the wireless environment.
 25. The system ofclaim 23 wherein: the group of wireless access points includes twowireless access points, the wireless access points each having aplurality of transceivers and a magnetometer that determines a spatialorientation the wireless access points; the distance module determines aplurality of distances between the station and individual transceiversin the plurality of transceivers based on the RSS information and theshadow fading factor; the localization module identifies a plurality oftriangular sub-regions of the wireless environment based on respectivespatial orientations of the individual transceivers and the respectivedistances between the station and the individual transceivers; and thelocalization module determines that one of the triangular sub-regions inthe plurality of triangular sub-regions is the sub-region in thewireless environment that the station is located in.
 26. The system ofclaim 25 wherein: individual triangular sub-regions in the plurality oftriangular sub-regions have vertices corresponding to a set of threecoordinates in the wireless environment; and individual coordinates inthe set of coordinates correspond to a spatial orientation of one of thetransceivers and a distance between the station and the transceiver. 27.The system of claim 25 wherein the localization module: determinesrespective areas for individual triangular sub-regions in the pluralityof triangular sub-regions; identifies a triangular sub-region in theplurality of triangular sub-regions having the smallest area; anddetermines that the triangular sub-region having the smallest area isthe triangular sub-region the station is located in.
 28. The system ofclaim 27 wherein the localization module: determines a center of thetriangular sub-region the station is located in; and identifies thecenter of the triangular sub-region the station is located in as thelocation that corresponds to the approximate location of the station inthe wireless environment.
 29. The system of claim 28 wherein the centerof the triangular sub-region the station is located in is thecircumcenter.
 30. The system of claim 25 wherein the localization moduledetermines the respective spatial orientations of individualtransceivers in the plurality of transceivers of the individual wirelessarrays based on orientation information received from the individualwireless arrays.